Detail

OffscreenWindow is strictly intended to be used for obtaining snapshots of widgets that are not
part of a normal widget hierarchy. It differs from widgetGetSnapshot in that the widget you
want to get a snapshot of need not be displayed on the user's screen as a part of a widget
hierarchy. However, since OffscreenWindow is a toplevel widget you cannot obtain snapshots of a
full window with it since you cannot pack a toplevel widget in another toplevel.

The idea is to take a widget and manually set the state of it, add it to a OffscreenWindow and
then retrieve the snapshot as a Pixmap or Pixbuf.

OffscreenWindow derives from Window only as an implementation detail. Applications should not
use any API specific to Window to operate on this object. It should be treated as a Bin that
has no parent widget.

When contained offscreen widgets are redrawn, OffscreenWindow will emit a damageEvent signal.

Constructors

Creates a toplevel container widget that is used to retrieve snapshots of widgets without showing
them on the screen. For widgets that are on the screen and part of a normal widget hierarchy,
widgetGetSnapshot can be used instead.